Three point charges are placed on the y-axis. a chage at q at y=a, a charge at -2q at the origin, and a charge q at y=-a. find the magnitude and direction of the electrif field on the y-axis for y>a I'm not sure where to begin at all. This is what I am thinking, but not completely sure. I could find the electric field the charges but I dont know how to encoporate the fact that there are two other charges that add to the electric field. any suggestions?